(a) Field of the Invention
The present invention relates to a switch control device, a power supply device including the same, and a control method thereof. Particularly, the present invention relates to a switch control device and a control method thereof for controlling a switching operation of a power switch under a soft start mode and a standby mode of a power supply device.
(b) Description of the Related Art
The power supply device is operated according to a soft start mode for preventing an in-rush current under initial operation and minimizing an output overvoltage. The soft start mode controls the switching operation of the power switch of the power supply device to gradually increase an output voltage at the initial operation of the power supply device. That is, the switching operation of the power switch is controlled for the output voltage of the power supply device to be gradually increased during a time that the power supply device is operated according to the soft start mode.
In general, an additional soft start circuit gradually increasing a soft start signal is required for controlling the power switch according to the soft start mode. The soft start circuit includes a plurality of resistors, a plurality of switches, a logic calculation circuit, an amplifier, and a counter. This is causes an increase in the size of the switch control device. The counter counts the passage of a time, the output signal of the logic calculation circuit is increased and amplified step by step according to the count result, and the switching operation of the plurality of switches is controlled according to the amplified signal. A predetermined voltage is divided into a plurality of voltages of various levels by the plurality of resistors, and one of the plurality of voltages is output as the soft start signal through the plurality of switches.
When the above soft start circuit increases the soft start signal by using the current source and the capacitor, the capacity of the capacitor must be large such that the circuit size to form the capacitor is increased. Accordingly, the soft start circuit is also large.
On the other hand, the output voltage is stabilized after the initial operation of the power supply device, and when the load that the power supply device supplies is small, the power supply device is operated according to the standby mode.
The power supply device executes the power switch switching operation during a predetermined period according to the feedback voltage to reduce the power consumption during the standby mode, and executes the burst operation stopping the switching operation during a predetermined period.
In the power supply device during the standby mode, the power consumed to control the switching operation of the power switch is relatively increased compared with the power supplied to the load.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.